JP4655597B2 - Image forming system - Google Patents

Description

  The present invention relates to an image forming system including an image forming apparatus such as a copying machine and a printer using an electrophotographic system, and a post-processing apparatus that performs processing such as punching, binding, and folding on an image-formed transfer material.

  In recent years, color image forming apparatuses for forming a color image based on various image information are known. Unlike black and white character images, color images are obtained by overlaying yellow, magenta, cyan, and black toner on a transfer material, and then heating and pressing the toners together. Therefore, the fixing temperature becomes higher than the fixing temperature in black-and-white image formation, and it takes time until the toner solidifies after fixing. Therefore, the toner on the next transfer material adheres to the toner on the already-transferred transfer material. In addition, since the total toner amount is large, the amount of WAX for preventing the toner from adhering to the heating roller and the pressure roller also increases, and the amount of WAX in the toner that oozes out on the toner surface also increases. Before the exuded WAX is completely solidified, it comes into contact with the conveying roller, the guide plate, etc., and is cooled and becomes cloudy, resulting in uneven glossiness in the image.

  As described above, the following techniques are known as techniques for solving the above-described problems in the color image forming apparatus.

In other words, in a fixing device that is used in a color image forming apparatus that forms a multicolor image on a transfer material and heats and pressurizes toner on the transfer material, at least one surface of the transfer material after passing through the fixing nip is cooled. A cooling unit is provided to cool the transfer material before discharging it to the paper discharge tray to prevent adhesion between the transfer materials (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-150677

  However, in recent years, it is known that post-processing such as perforation, folding, and stapling is performed on an image-formed transfer material. However, Patent Document 1 discloses image formation including an image forming apparatus and a post-processing apparatus. There is no description or suggestion regarding cooling of the transfer material after fixing in the system.

  Generally, in the post-processing apparatus, it takes time to perform each post-processing, and the post-processing is performed after ensuring the time required for processing by increasing the speed of the image-formed transfer material and widening the interval between the transfer materials. It is configured as follows.

  Thus, even if a cooling means is provided on the downstream side of the fixing nip portion in order to increase the speed in the post-processing apparatus, the degree of cooling of the transfer material changes from the middle of the transfer material. The degree of cooling changes and the image becomes uneven.

  Further, in the post-processing apparatus, since processing is performed in an accelerated state, the nip pressure of the transport roller must be increased, or the guide plate must be bent in order to perform each process structurally. Or contact with the guide plate may cause WAX unevenness.

  In view of the above-described problems, an object of the present invention is to provide an image forming system having an image forming apparatus and a post-processing apparatus capable of obtaining a high-quality image without image unevenness.

  The object of the present invention can be achieved by the following constitution.

(1) an image forming unit for forming a toner image on a transfer material;
A fixing device provided on the downstream side of the image forming unit in the transfer material conveyance direction for melting and fixing an unfixed toner image on the transfer material;
First conveying means provided on the downstream side of the fixing device in the transfer material conveying direction;
Detecting means for detecting a transfer material passing between the fixing device and the first conveying means;
A cooling means provided on the downstream side in the transfer material conveyance direction of the first conveyance means, and for cooling the transfer material;
Second conveying means provided downstream of the cooling means in the transfer material conveying direction;
A post-processing device that is provided downstream of the second transport means in the transfer material transport direction and performs post-processing on the transfer material on which the toner image is formed;
Control means for controlling the transport speed of the second transport means;
Have
The control means controls the transfer material conveyance speed of the second conveyance means to be the same speed as the transfer material conveyance speed of the first conveyance means while the transfer material passes through the cooling region of the cooling means ,
A first mode for controlling the second conveying means to speed up after the trailing edge of the transfer material has passed through the detecting means; and the second conveying means for speeding up after the transfer material has passed through the cooling region. An image forming system, wherein the second mode to be controlled can be switched.

( 2 ) The post-processing apparatus includes a shift unit that shifts the transfer material in a direction orthogonal to the transfer material conveyance direction every predetermined number of sheets , a punching unit that punches a predetermined position of the transfer material, and a plurality of transfer materials. The image forming system according to (1 ), further comprising at least one of a stapling unit that binds the sheet, a folding unit that folds the transfer material, and a sheet insertion unit that inserts a slip sheet or a cover sheet.

  By making the paper transport speeds of the first transport means and the second transport means across the cooling area the same, the paper transport speed does not change during cooling, so the paper carrying the toner that is not completely fixed after fixing passes. Even so, the toner and the WAX that has oozed out on the toner surface are uniformly and sufficiently fixed by the cooling means in the entire area of the paper, so that an image without unevenness can be obtained.

  In addition, by sufficiently cooling, it is possible to prevent the WAX that has oozed out on the toner surface from being suddenly cooled and becoming cloudy unevenness by contacting the conveyance roller or guide plate of the post-processing apparatus. become.

  In particular, when the total amount of toner on the paper is large, such as a color image, the total amount of WAX that has oozed out on the toner and the toner surface also increases, but there is no unevenness by cooling uniformly and sufficiently by the cooling means. A high-quality color image can be obtained.

  Hereinafter, an example of an embodiment of the present invention will be described. The description in this section does not limit the technical scope of the claims or the meaning of terms, and the assertive explanation in the embodiments of the present invention below shows the best mode, and It does not limit the meaning or technical scope of the terms of the invention.

  First, an image forming apparatus constituting an image forming system according to the present invention will be described with reference to FIG.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus.

  In addition, in the following description including FIG. 1, the same number is attached | subjected to the member which has the same function and structure.

  According to FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading apparatus SC provided on the upper part of the image forming apparatus main body GH.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and arranges image forming units that form yellow, magenta, cyan, and black color toner images along the moving direction of the intermediate transfer member. The color toner image formed on the image carrier of each image forming unit is transferred onto the intermediate transfer member and superimposed, and then transferred onto a transfer material (hereinafter referred to as paper) at a time.

  In the figure, an analog signal scanned and exposed by an optical system on a document image placed on the image reading device SC, read into a line image sensor CCD, and photoelectrically converted by the line image sensor CCD is converted into an analog signal by an image processing unit. After processing, A / D conversion, shading correction, image compression processing, and the like are performed, they are sent to the writing means 3 as image writing means.

  In the figure, four sets of processes for forming images for each color of yellow (Y), magenta (M), cyan (C) and black (K) are provided on the peripheral edge of the intermediate transfer belt 6 as an intermediate transfer body. The unit 100 is arranged in the order of Y, M, C, K in the vertical direction along the intermediate transfer belt 6 in the rotation direction of the intermediate transfer belt 6 in the vertical direction indicated by the arrows in the drawing as a unit for forming a color toner image. ing.

  The four process units 100 have a common structure, and each has a photosensitive drum 1 as an image carrier, a charger 2 as a charging unit, a writing unit 3 as an image writing unit, and a developing unit. And a photoconductor cleaning device 190 as an image carrier cleaning means.

  The photosensitive drum 1 is an organic material having a layer thickness (film thickness) of about 20 to 40 μm as a photosensitive layer on the outer periphery of a cylindrical substrate formed of a metallic member such as aluminum having an outer diameter of about 40 to 100 mm. A photoconductive layer (OPC) is formed. The photosensitive drum 1 is rotated in the direction indicated by the arrow.

  Around the photosensitive drum 1, an image forming unit including a charger 2, a writing unit 3, and a developing device 4 as a set is arranged in the rotation direction of the photosensitive drum 1 indicated by an arrow in the drawing.

  The charger 2 is attached in close proximity to the photosensitive drum 1 in a direction orthogonal to the moving direction of the photosensitive drum 1 (in the direction perpendicular to the paper surface in the drawing). The charger 2 includes a discharge wire as a corona discharge electrode that applies a predetermined potential to the organic photosensitive layer of the photosensitive drum 1, and performs charging action by corona discharge having the same polarity as the toner. A uniform potential is applied.

  The writing means 3 rotationally scans laser light emitted from a semiconductor laser (LD) light source (not shown) in the main scanning direction by a rotating polygon mirror (no symbol), an fθ lens (no symbol), a reflection mirror (no symbol) ) And the like, exposure (image writing) is performed on the photosensitive drum 1 with an electric signal corresponding to the image signal, and an electrostatic latent image corresponding to the original image is formed on the photosensitive layer on the surface of the photosensitive drum 1. .

  The developing device 4 accommodates a two-component developer of each color of yellow (Y), magenta (M), cyan (C) or black (K) charged to the same polarity as the charging polarity of the photosensitive drum 1, A developing roller 4a which is a developer carrying member is provided. The developing roller 4a is kept in a predetermined gap from the photosensitive drum 1 by an abutment roller (not shown), and rotates in the forward direction and the rotational direction of the photosensitive drum 1. During development, the developing roller 4a On the other hand, by applying a DC voltage having the same polarity as that of the toner or a developing bias voltage in which an AC voltage is superimposed on the DC voltage, reversal development is performed on the exposed portion on the photosensitive drum 1.

  The intermediate transfer belt 6 is a semiconductive endless (seamless) resin belt member having a volume resistivity of about 1E + 7 to 1E + 9 Ω · cm and a surface resistivity of about 1E + 10 to 1E + 12 Ω / □. The intermediate transfer belt 6 is wound around a plurality of roller members including a tension roller 6a, and is supported rotatably in a vertical method. It is also possible to use a drum-shaped intermediate transfer member.

  The primary transfer roller 7 as a first transfer unit for each color is made of a roller-like conductive member using foamed rubber such as silicon or urethane, and a photosensitive drum for each color with the intermediate transfer belt 6 interposed therebetween. 1, and the back surface of the intermediate transfer belt 6 is pressed to form a transfer area with the photosensitive drum 1. A DC constant current having a polarity opposite to that of the toner is applied to the primary transfer roller 7 by constant current control, and the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a transfer electric field formed in the transfer area. The

  The image forming process (image forming process) will be described below.

  When the image recording is started, the photosensitive drum drive motor (not shown) is rotated to rotate the Y photosensitive drum 1 in the direction indicated by the arrow in the figure, and a potential is applied to the Y photosensitive drum 1 by the Y charger 2. . After the Y photosensitive drum 1 is applied with a potential, the Y writing means 3 performs exposure (image writing) with an electric signal corresponding to the first color signal, that is, the Y image data. An electrostatic latent image corresponding to a yellow (Y) image is formed on the drum 1. The latent image is reversely developed by the Y developing device 4 to form a toner image made of yellow (Y) toner on the Y photosensitive drum 1. The Y toner image formed on the Y photosensitive drum 1 is transferred onto the intermediate transfer belt 6 by a primary transfer roller 7 as a primary transfer means.

  By a similar process, magenta (M), cyan (C), and black (K) toner images are sequentially formed on the intermediate transfer belt 6 in a superimposed manner.

  The toner remaining on the peripheral surface of each photoreceptor drum 1 after the transfer is cleaned by the photoreceptor cleaning device 190.

  On the other hand, the paper S as a transfer material accommodated in the paper feed cassettes 20A, 20B, and 20C is fed by the feed roller 21 and the paper feed roller 22A provided in the paper feed cassettes 20A, 20B, and 20C, respectively, and is transported. The transfer area of the secondary transfer roller 7A as a secondary transfer means conveyed by 22B, 22C, 22D, conveyed by the registration roller 23 in synchronization with the writing timing of the writing means 3, and applied with a voltage of the opposite polarity to the toner. 2, the superimposed color toner images formed on the intermediate transfer belt 6 are transferred together.

  The sheet S on which the color image has been transferred is melted and fixed by the fixing device 17 and further conveyed by the first conveying means 18 and sent to the post-processing device. Reference numeral 19 denotes a cooling unit that cools the sheet S that has been subjected to the fixing process while it is being fed into the post-processing apparatus. The details of the fixing device 17, the first conveying unit 18, and the cooling unit 19 will be described later.

  Further, after the color image is transferred onto the paper S by the secondary transfer roller 7A, the residual toner is removed from the intermediate transfer belt 6 which has separated the curvature of the paper S by the intermediate transfer body cleaning device 190A.

  9A is an image forming apparatus operation display means, and 9B is an image forming apparatus control means.

  In the description of the image forming apparatus, the color image formation is described. However, the present invention includes a case where a monochrome image is formed.

  Next, a post-processing apparatus constituting the image forming system will be described with reference to FIG.

  FIG. 2 is a schematic configuration diagram of the post-processing apparatus.

  As shown in the figure, the post-processing device FS includes a sheet feeding tray 10 on which an interleaf or cover sheet T is placed on the upper stage, a sheet feeding means 20, and a fixed discharge tray 40. A punching unit 30 for performing punching processing on the sheet T, a shift unit 90, and a stapling unit 503 for performing stapling processing on a sheet in which the sheet T is inserted into the sheet S and a folding unit 70 are provided on the lower stage.

  On the left side of the post-processing device FS in the figure, a sheet stacking means 60 that can be raised and lowered for stacking sheets S or a bundle of sheets Sa that has been stapled, and an origami stacking means for stacking the folded sheet bundle Sa. 80 is arranged.

  A post-processing device operation display means 10A and a post-processing device control means 10B are provided in the upper left stage of the post-processing device FS.

  Next, the details of the post-processing device FS having the above-described configuration will be described along the flow of the sheet S and the sheet T, using FIG.

  The sheets T set in the sheet feeding tray 10 are fed one by one by the sheet feeding unit 20.

  The fed sheet T is transported by transport rollers, guide plates and the like (without reference numerals) that form the transport path R1, and joins at the confluence point C to the transport path R2 of the paper S discharged from the image forming apparatus GS. It is transported along the transport path R2.

  In the following description, when the conveyance of the paper S and the sheet T is described, only the conveyance path will be described, and the conveyance rollers and the like that form the conveyance path will be omitted except those that need to be specifically described. And Further, the paper S and the sheet T are simply represented by the paper S.

  The paper S on the transport path R2 is stopped by the punching means 30 disposed on the downstream side of the junction C with the rear end side in the transport direction of the paper S as a reference position, and a hole for a file is punched at a predetermined position. Processing is performed.

  The punched paper S is transported through the transport path R2 and reaches the switching gate G1.

  When simple discharge is selected on the operation display means 9A, the switching gate G1 is set to a position indicated by a dotted line in the figure by driving a solenoid (not shown), and the sheet S passes through the conveyance path R3 and is fixedly discharged to the fixed discharge table 40. The paper is discharged.

  When the switching gate G1 is selected in the state of the solid line position shown in the drawing, the sheet S proceeds on the transport path R2 as it is and reaches the switching gate G2.

  When the stapling process is selected in the image forming apparatus operation display means 9A or the post-processing apparatus operation display means 10A, the switching gate G2 is set to the position indicated by the solid line in the figure by driving a solenoid (not shown), and the sheet S is conveyed in the transport path R4. Then, as shown in the figure, the conveying roller 703 discharges upward along the paper placing table 501 having an upwardly inclined slope as shown in the figure. It slides and descends on the inclined surface, hits against the binding butting plate 502, and is placed with the rear end side in the transport direction as the reference position.

  When the number of sheets S placed on the sheet placing table 501 reaches a predetermined number, the stapling unit 503 performs stapling processing at a predetermined position. When the stapling process is completed, the pulley is arranged so as to be parallel to the sheet placing table 501. The belt 506 stretched between the belts 504 and 505 is rotated, and the sheet bundle Sa composed of the sheets S is moved upward along the sheet placing table 501 by the sheet discharge claw 507 fixed to the belt 506, and is moved on the transport path R2. The paper is discharged onto the paper discharge stacking means 60 by a paper discharge roller 704 provided on the paper.

  When the folding process is selected, when the number of sheets S placed on the sheet placing table 501 reaches a predetermined number, the binding abutting plate 502 is retracted, and the sheet S slides and descends to be placed on the folded sheet placing table 701. The folding knife 702 is pushed into the pair of folding rollers 703 to perform the folding process. The sheet S that has been subjected to the folding process is conveyed obliquely downward to the left in the drawing and stacked on the origami stacking means 80.

  When the switching gate G2 is set at the dotted line position shown in the drawing, the paper S is transported on the transport path R2, and is shifted and shifted by the shift means 90 in a direction orthogonal to the paper transport direction every predetermined number of sheets. In this way, the paper is discharged to the paper discharge stacking means 60 that can be moved up and down.

  The punching process by the punching unit 30, the binding process by the stapling unit 503, the folding process by the folding unit 70, and the shift process by the shift unit 90 are performed by temporarily stopping the conveyed paper S. Therefore, when the above processing is performed on the paper S, the interval between the papers S is controlled to be wide.

  Which process is performed is selected from one of the operation display means of the image forming apparatus and the post-processing apparatus, and is controlled by the control means.

  Next, cooling of the sheet after fixing, which is a feature of the present invention, will be described with reference to FIG.

  FIG. 3 is a detailed view showing the cooling process of the sheet after leaving the fixing device.

  The fixing device 17 is in contact with the surface of the fixing roller 171, a pressure roller 172 in contact with the fixing roller 171 by a spring (not shown), a halogen heater 173 built in the fixing roller 171, and the surface of the fixing roller 171. It consists of the thermistor 174 and the like.

  The fixing roller 171 is made of a metal core whose surface is covered with silicon rubber, fluorine rubber or the like, and the pressure roller 172 is made of a metal core whose surface is covered with silicon rubber.

  The thermistor 174 detects the surface temperature of the fixing roller 171, and the detection signal is used for operation control of the halogen heater 173.

  PS is a detection means including a photoelectric reflection type sensor installed on the downstream side in the sheet conveyance direction as viewed from the nip formed by the fixing roller 171 and the pressure roller 172, and detects the leading edge or trailing edge of the sheet S. The detection signal is used for jam detection in the fixing device, transport speed control of the paper S after fixing, and the like.

  The first transport unit 18 includes a pair of transport rollers 181 and 182, a spur 183, and the like installed on the downstream side in the sheet transport direction as viewed from the nip formed by the fixing roller 171 and the pressure roller 172. The sheet conveying speed is equal to the sheet conveying speed in the nip portion.

  Reference numeral 184 denotes a switching gate, and when it is at the position of the solid line in the figure, the sheet S after fixing is directly conveyed to the post-processing device FS by the conveying rollers 181 and 182 and the spur 183.

  When the paper S is to be reversed and discharged, or when image formation is to be performed on the back side of the paper S, the switching gate 184 is moved between a solid line position and a dotted line position in the figure by a predetermined timing by a solenoid (not shown). It is performed by rocking with.

  The cooling unit 19 includes a blower fan 191, a duct 192, and the like, and the air outside the image forming apparatus is taken in by the rotation of the blower fan 191, and the paper is transported at the conveyance roller 182 that is a cooling region and the junction C. The sheet S, which is blown between the conveyance roller 121 installed on the downstream side in the direction and passes through the cooling region, is cooled.

  The cooled sheet S is conveyed downstream by the conveying roller 121. Normally, in order to ensure the productivity of the image forming system, when the trailing end of the sheet S passes the detection unit PS, the first conveying unit is used. Control is performed so that the sheet conveying speed of the second conveying means 120 including the conveying roller 121 set to be equal to the 18 sheet conveying speed and the conveying roller downstream thereof is increased.

  However, in this case, the speed at which the paper S passes through the cooling area is different between the leading edge area and the trailing edge area, so that the degree of cooling is different and the image is uneven.

  Further, since the toner after fixing is not completely fixed, when the rear end side that has not been sufficiently cooled comes into contact with, for example, the conveyance roller or the guide plate of the second conveyance unit 120, The exuded WAX is rapidly cooled and becomes cloudy unevenness.

  In order to avoid such image unevenness, in this embodiment, control can be performed so that image formation can be performed with priority over productivity, and this control will be described with reference to FIGS. 4 and 5.

  FIG. 4 is a block diagram showing the control relationship of the image forming system, and FIG. 5 is a flowchart showing selection of productivity priority or image quality priority.

  The image forming apparatus control means 9B is composed of a storage means (ROM, RAM) for storing control procedures and various data of the image forming apparatus, a CPU for executing control based on the control procedures and data stored in the storage means, and the like. Has been.

  The image forming apparatus operation display means 9A performs operations such as setting the number of copies, starting an image forming operation, or detecting abnormality.

  Reference numeral 3A denotes writing means driving means for driving a polygon motor or the like, which operates according to a command from the image forming apparatus control means 9B to drive the writing means 3.

  A sheet feeding unit driving motor 23A operates according to a command from the image forming apparatus control unit 9B to drive the sheet feeding unit (registration roller) 23.

  Reference numeral 18A denotes a first transport unit driving motor which operates according to a command from the image forming apparatus control unit 9B and drives the first transport unit 18.

  The detection means PS detects the leading edge and the trailing edge of the paper S, and the detection signal is sent to the image forming apparatus control means 9B.

  The post-processing device control means 10B is composed of storage means (ROM, RAM) for storing the control procedure of the post-processing device and various data, and a CPU for executing control based on the control procedure and data stored in the storage means. The image forming apparatus control unit 9B is communicably coupled.

  The post-processing device operation display means 9A displays post-processing means selection, abnormality detection, and the like.

  Reference numeral 120A denotes a second transport unit driving motor, which operates according to a command from the post-processing device control unit 10B and drives the second transport unit 120.

  Here, the second transport unit 120 refers to a transport roller including a transport roller 121 necessary for transporting the paper S in all transport paths in the post-processing apparatus.

30A is a punching means driving means, 50A is a stapling means driving means, 70A is a folding means driving means, and 90A is a shift means driving means. 50, the folding means 70, and the shift means 90 are driven.

  The control of the post-processing apparatus is started based on a detection signal that the detection unit PS detects the trailing edge of the paper S.

  Next, a flowchart for performing image formation and post-processing after selecting whether to prioritize productivity or image quality when performing image formation on the paper S will be described with reference to FIG.

  First, on the image forming apparatus operation display means 9A, any one of (1) productivity priority mode, (2) first image quality priority mode, (3) second image quality priority mode, and (4) third image quality priority mode is selected. In addition to selection, setting of the number of image forming copies and which post-processing to perform are selected (ST1). The post-processing selection may be performed from the post-processing operation display means 10A.

  Here, each priority mode will be described with reference to FIG.

  (1) Productivity priority mode: This mode prioritizes the productivity of the image forming system. After the trailing edge of the paper S is detected by the detection means PS, the speed is increased by the first conveyance means 18 and the second conveyance means 120. Then carry out the specified post-processing device.

  The transport speed when the second transport means 120 is increased is set to a transport speed at which a space between sheets necessary for each post-processing device to perform post-processing is obtained. The transport speed of the second transport means 120 when the speed is increased can be obtained by timing design or the like.

  (2) First image quality priority mode; one of the modes in which image unevenness does not occur on the paper passing through the cooling region. The image forming is performed by adjusting the conveying speed of the second conveying means 120 to the conveying speed of the first conveying means 18. The conveyed sheet S is transported along the transport path R2 of the post-processing apparatus, and is discharged outside the apparatus without performing post-processing.

(3) Second image quality priority mode; this is one of the modes in which image unevenness does not occur on the paper passing through the cooling region, and the conveyance speed of the second conveyance means 120 is matched to the conveyance speed of the first conveyance means 18;
At the same time as the writing interval of the writing means 3 (see FIG. 1) is widened, the paper feeding interval of the paper feeding means 23 (see FIG. 1) is correspondingly increased to form an image. The designated post-processing apparatus is performed while being conveyed by the conveying means 120. The transport speed of the second transport means 120 is the same as the transport speed of the first transport means 18.

  (4) Third image quality priority mode; one of the modes in which image unevenness does not occur on the paper passing through the cooling region, and is specified by increasing the transport speed of the second transport means 120 after the paper passes through the cooling region. The post-processing apparatus is performed. The speed of the second transport unit 120 is increased when the trailing edge of the paper S passes the transport roller 121.

  When the mode selection or the like is made by the image forming apparatus operation display means, in the next step (ST2), it is determined whether or not it is in the productivity priority mode. If YES, the first conveying means 18 and the second conveying means 120 are turned on. The speed is increased (ST3), image formation (ST4), and post-processing apparatus (ST5) are performed to determine whether or not a predetermined number of copies has been reached (ST6), and ST4 and ST5 are repeated until the predetermined number of copies is reached.

  If NO in ST2, it is determined whether the mode is the first image quality priority mode (ST7). If YES, the transport speed of the second transport means 120 is adjusted to the transport speed of the first transport means 18 (ST8), and cooling is performed. The means 19 is actuated (ST9), image formation is performed (ST10), the cooled sheet S is transported through the transport path R2 of the post-processing apparatus, and discharged outside the apparatus without performing post-processing (ST11). It is determined whether the number of copies has been reached (ST12), and ST10 and ST11 are repeated until the predetermined number of copies is reached.

  In ST7, if NO, it is determined whether the second image quality priority mode is selected (ST13). If YES, the transport speed of the second transport unit 120 is matched with the transport speed of the first transport unit 18 (ST14). Then, the cooling means 19 is activated (ST15), and the writing interval of the writing means 3 is widened (ST16). At the same time, the paper feeding interval of the paper feeding means 23 is correspondingly widened (ST17) to perform image formation (ST18). ), The designated post-processing apparatus is carried out while the image-formed paper is conveyed by the second conveying means 120 (ST19). It is determined whether or not the number of processed copies has reached a predetermined number of copies (ST20), and ST18 and ST19 are repeated until the predetermined number of copies is reached.

If NO in ST13, the cooling means 19 is activated (ST21), image formation is performed (ST22), and whether or not the image-formed paper has passed the cooling area, that is, the trailing edge of the paper S is detected. It is determined whether or not a predetermined time has elapsed after being detected by the means PS (ST23). If YES, the transport speed of the second transport means 120 is increased (ST24) and predetermined post-processing is performed (ST25). It is determined whether or not the predetermined number of copies has been reached (ST26), and the operations of ST22, ST23, ST24 and ST25 are repeated until the predetermined number of copies is reached.

  In addition, the conveyance speed of the 2nd conveyance means 120 can be changed by driving the conveyance roller 121 with a stepping motor and changing the rotation speed of a stepping motor, for example.

  Various data necessary for control, for example, write interval data by the writing unit 3 is stored in advance in the storage unit of the image forming apparatus control unit 9B, and is called on the CPU as necessary to execute the program. I can do it.

  As described above, the operator can select either the productivity priority mode or the image quality priority mode.

  When the image quality priority mode is selected, the paper transport speed does not change during cooling by making the paper transport speeds of the first transport means and the second transport means across the cooling area the same. Even if a sheet carrying toner is passed, the toner and the WAX that has oozed out on the toner surface are uniformly and sufficiently fixed by the cooling means in the entire area of the sheet, so that a uniform image can be obtained. I can do it.

  Further, by sufficiently cooling, it is possible to prevent the WAX that has come into contact with the conveyance roller and the guide plate of the post-processing apparatus and oozed out on the toner surface from being rapidly cooled to become cloudy unevenness. it can.

  In particular, when the total amount of toner on the paper is large as in a color image, the total amount of WAX that has oozed out on the toner and the toner surface also increases. However, the cooling means can uniformly and sufficiently cool the unevenness. High-quality images can be obtained.

  Further, by providing the cooling unit on the image forming apparatus side as in the present embodiment, even when connected to a plurality of post-processing apparatuses, it is possible to cope with a single cooling unit, so that the cost can be reduced.

  Note that the image forming apparatus and the post-processing apparatus may be provided integrally, or the image forming apparatus control means and the post-processing apparatus control means may be provided integrally.

1 is a schematic configuration diagram of an image forming apparatus. The schematic block diagram of a post-processing apparatus. FIG. 4 is a detailed view showing a cooling process of a sheet after exiting the fixing device. FIG. 3 is a block diagram showing a control relationship of the image forming system. The flowchart which shows selection of productivity priority or image quality priority.

Explanation of symbols

GS image forming apparatus FS post-processing apparatus PS detection means S paper 10 sheet feeding tray 17 fixing device 18 first conveying means 19 cooling means 20 sheet feeding means 30 punching means 40 fixed discharge table 70 folding means 90 shifting means 120 first 2 conveying means 503 stapling means 9A image forming apparatus operation display means 9B image forming apparatus control means 10A post-processing apparatus operation display means 10B post-processing apparatus control means

Claims (2)

An image forming unit for forming a toner image on a transfer material;
A fixing device provided on the downstream side of the image forming unit in the transfer material conveyance direction for melting and fixing an unfixed toner image on the transfer material;
First conveying means provided on the downstream side of the fixing device in the transfer material conveying direction;
Detecting means for detecting a transfer material passing between the fixing device and the first conveying means;
A cooling means provided on the downstream side in the transfer material conveyance direction of the first conveyance means, and for cooling the transfer material;
Second conveying means provided downstream of the cooling means in the transfer material conveying direction;
A post-processing device that is provided downstream of the second transport means in the transfer material transport direction and performs post-processing on the transfer material on which the toner image is formed;
Control means for controlling the transport speed of the second transport means;
Have
The control means controls the transfer material conveyance speed of the second conveyance means to be the same speed as the transfer material conveyance speed of the first conveyance means while the transfer material passes through the cooling region of the cooling means ,
A first mode for controlling the second conveying means to speed up after the trailing edge of the transfer material has passed through the detecting means; and the second conveying means for speeding up after the transfer material has passed through the cooling region. An image forming system, wherein the second mode to be controlled can be switched.   The post-processing apparatus includes a shift unit that shifts a transfer material in a direction orthogonal to the transfer material conveyance direction every predetermined number of sheets, a punching unit that punches a predetermined position of the transfer material, and a staple that binds a plurality of transfer materials. 2. The image forming system according to claim 1, further comprising at least one of: a means for folding the transfer material; a sheet inserting means for inserting a slip sheet or a cover sheet.

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